This disclosure relates to a switch, a charge monitoring apparatus and a rechargeable battery module.
As represented by a lithium-ion battery pack, a charging apparatus which can repetitively carry out charging and discharging is known. Generally, the charging apparatus includes a rechargeable battery cell unit formed from a plurality of rechargeable battery cells connected in series. If charging and discharging of the rechargeable battery cell unit are carried out, then the rechargeable battery cells which configure the rechargeable battery cell unit are charged and discharged and the charged state of each rechargeable battery cell varies. At this time, the charged state of the rechargeable battery cells sometimes exhibits a dispersion among the cells. To repeat charging and discharging of the rechargeable battery cells while the charged state of them exhibits a dispersion leads to reduction of the life span of the rechargeable battery cells and hence of the life span of the entire rechargeable battery cell unit and therefore is not desirable. Therefore, a method has been proposed to monitor the charged state of each of rechargeable battery cells which configure a rechargeable battery cell unit and control charging and discharging of each rechargeable battery cell in response to the charged state of the rechargeable battery cell. The method is disclosed, for example, in Japanese Patent No. 3829453.
In order to achieve reduction in size and cost of a monitoring circuit for monitoring the charged state of a rechargeable battery cell, it is desired to form the monitoring circuit as an LSI (Large Scale Integration). In order to form the monitoring circuit as an LSI, it is desired to configure a switch for changing over a rechargeable battery cell to be monitored by a transistor or the like. JP-T-2006-507790 discloses a configuration wherein a switch for changing over a rechargeable battery cell to be monitored is configured from a transistor.